Backlight unit and liquid crystal display device including the same

ABSTRACT

A backlight unit for a liquid crystal display device including a liquid crystal panel, includes: a light source including a light-emitting diode (“ED”) which generates and emits light; and a light converting layer between the light source and the liquid crystal panel, spaced apart from the light source, and converting the light from the light source into white light and emitting the white light toward the liquid crystal panel. The light converting layer includes: semiconductor nanocrystals, and a barrier material which restricts penetration of moisture or oxygen.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 14/010,718 filed Aug. 27, 2013 and issued as U.S. Pat. No. 9,606,281on Mar. 28, 2017, which claims priority to and the benefit of KoreanPatent Application No. 10-2012-0099549, filed on Sep. 7, 2012, in theKorean Intellectual Property Office, the disclosure of which isincorporated herein in its entirety by reference.

BACKGROUND

1. Field

Provided is a backlight unit using light-emitting diodes (“LEDs”) as alight source and liquid crystal display (“LCD”) devices including thebacklight unit.

2. Description of the Related Art

Unlike plasma display panels (“PDPs”) and field emission display (“FED”)devices, liquid crystal display (“LCD”) devices are light-receivingdisplay devices that may form an image by receiving external lightinstead of using light generated and emitted therein. Accordingly, LCDdevices include backlight units that are disposed on rear surfaces ofthe LCD devices and emit light.

Backlight units for conventional LCD devices use cold cathodefluorescent lamps (“CCFLs”) as light sources. However, in this case,color purity may decrease and it is more difficult to achieve uniformityin brightness as sizes of the conventional LCD devices increase.

SUMMARY

Provided is a backlight unit using light-emitting diodes (“LEDs”) as alight source and a liquid crystal display (“LCD”) device including thebacklight unit.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

Provided is a backlight unit for a LCD device including a liquid crystalpanel, including: a light source including a LED which generates andemits light; and a light converting layer between the light source andthe liquid crystal panel, and spaced apart from the light source. Thelight converting layer converts the light from the light source intowhite light and emits the white light toward the liquid crystal panel.The light converting layer includes semiconductor nanocrystals, and abarrier material which restricts penetration of moisture or oxygen.

The light converting layer may further include a transparent substrate,a light converting film on a surface of the transparent substrate andincluding the semiconductor nanocrystals, and a barrier layer on asurface of the light converting film and including the barrier material.The barrier layer may also be on a surface of the transparent substrate,opposite to the surface of the light converting film.

The light converting layer may further include a light converting filmincluding the semiconductor nanocrystals, and a barrier layer on asurface of the light converting film and including the barrier material.

The light converting layer may further include a light converting filmincluding the semiconductor nanocrystals and the barrier material.

The light converting layer may further include a barrier layer on asurface of the light converting film and including the barrier material.

The barrier material in the light converting film may restrictpenetration of one of the moisture or the oxygen, and the barriermaterial in the barrier layer may restrict the other of the moisture andthe oxygen.

A moisture transmission rate or an oxygen transmission rate of thebarrier material may be equal to or less than about 0.1 cubic centimeterper square meter per day (cc/m²/day).

The backlight unit may further include a plurality of light convertinglayers which converts the light into light of different colors. Theplurality of light converting layers may be arranged to have an emissionwavelength with lower energy as a distance from the light sourcedecreases. The plurality of light converting layers may be spaced apartfrom one another, and a blank layer may be defined between adjacentlight converting layers of the plurality of light converting layers.

The barrier material may include at least one selected from an organicmaterial and an inorganic material. The barrier material may include theorganic material and the inorganic material repeatedly alternated in astack. The organic material may include at least one selected fromthiolene, hybrid epoxy, polyurea, polytetrafluoroethylene (“PTFE”),polydimethylsiloxane (“PDMS”), polyvinylchloride, polycarbonate,polystyrene, polyimide, parylene, polyethylacrylate andpolymethylmethacrylate, and the inorganic material may include at leastone selected from silicon oxide, aluminum oxide, titanium oxide, indiumoxide, tin oxide, indium oxide, tantalum oxide, zirconium oxide andniobium oxide.

The backlight unit may further include a diffusive plate between thelight source and the light converting layer, or between the lightconverting layer and the liquid crystal panel. The light convertinglayer may contact a surface of the diffusive plate.

The light converting layer may further include light diffusing particleswhich diffuse the light.

The light converting layer may further include a light-convertingdiffusive film including the semiconductor nanocrystals and the lightdiffusing particles, and a barrier layer on a surface of thelight-converting diffusive film and including the barrier material.

The light converting layer may further include a light-convertingdiffusive film including the semiconductor nanocrystals, the barriermaterial and the light diffusing particles.

The light converting layer may further include a barrier layer on asurface of the light-converting diffusive film and including the barriermaterial.

An adhesive layer including the barrier material may be on a sidesurface of the light converting layer.

The backlight unit may further include a light guide plate between thelight source and the light converting layer. The light guide plateguides the light toward the light converting layer.

The light guide plate may include a light emitting first surface, asecond surface opposite to the light emitting first surface, and a sidesurface connecting the first and second surfaces to each other. Thelight source may face the side surface of the light guide plate.

The backlight unit may further include an optical sheet between thelight source and the liquid crystal panel. The optical sheet may includeat least one selected from a prism sheet, a brightness enhancement sheetand a micro-lens sheet.

The light source may emit blue light or ultraviolet light. The lightsource may include a substrate, and a plurality of LEDs on thesubstrate.

Provided is a backlight unit for a LCD device including a liquid crystalpanel, including: a light source including a LED which generates andemits light; a light guide plate between the light source and the liquidcrystal panel, and including semiconductor nanoparticles which convertthe light into white light, the light guide plate guiding the light fromthe light source toward the liquid crystal panel; and a barrier layer ona surface of the light guide plate, and including a barrier materialwhich restricts penetration of moisture or oxygen.

The light guide plate may include a light emitting first surface, asecond surface opposite to the light emitting first surface, and a sidesurface connecting the first and second surfaces to each other, and thelight source may face the side surface of the light guide plate.

The backlight unit may further include a diffusive plate between thelight guide plate and the liquid crystal panel. The light guide platemay further include light diffusing particles which diffuse the light.

The backlight unit may further include an adhesive layer on a sidesurface of the light guide plate, and including the barrier material.

Provided is a LCD device including: a light source including a LED whichgenerates and emits light; a light converting layer spaced apart fromthe light source, the light converting layer converting the light fromthe light source into white light and outputting the white light towarda liquid crystal panel, the light converting layer including:semiconductor nanoparticles, and a barrier material which restrictspenetration of moisture or oxygen; and the liquid crystal panel whichforms an image using the white light from the light converting layer.

Provided is a LCD device including: a light source comprising a LEDwhich generates and emits light; a light guide plate includingsemiconductor nanocrystals which convert the light into white light, thelight guide plate guiding the light from the light source toward aliquid crystal display panel; a barrier layer on a surface of the lightguide plate, and including a barrier material which restrictspenetration of moisture or oxygen; and the liquid crystal panel whichforms an image using the white light from the light guide plate.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings in which:

FIG. 1 is a cross-sectional view illustrating an embodiment of a liquidcrystal display (“LCD”) device;

FIG. 2 is a cross-sectional view illustrating another embodiment of alight converting layer of FIG. 1;

FIG. 3 is a cross-sectional view illustrating another embodiment of thelight converting layer of FIG. 1;

FIG. 4 is a cross-sectional view illustrating another embodiment of thelight converting layer of FIG. 1;

FIG. 5 is a cross-sectional view illustrating another embodiment of thelight converting layer of FIG. 1;

FIG. 6 is a cross-sectional view illustrating another embodiment of thelight converting layer of FIG. 1;

FIG. 7 is a cross-sectional view illustrating another embodiment of thelight converting layer of FIG. 1;

FIG. 8 is a cross-sectional view illustrating another embodiment of thelight converting layer of FIG. 1;

FIG. 9 is a cross-sectional view illustrating another embodiment of anLCD device;

FIG. 10 is a cross-sectional view illustrating another embodiment of anLCD device;

FIG. 11 is a cross-sectional view illustrating an embodiment of alight-converting diffusive layer of FIG. 10;

FIG. 12 is a cross-sectional view illustrating another embodiment of thelight-converting diffusive layer of FIG. 10;

FIG. 13 is a cross-sectional view illustrating another embodiment of thelight-converting diffusive layer of FIG. 10;

FIG. 14 is a cross-sectional view illustrating another embodiment of thelight-converting diffusive layer of FIG. 10;

FIG. 15 is a cross-sectional view illustrating another embodiment of thelight-converting diffusive layer of FIG. 10;

FIG. 16 is a cross-sectional view illustrating another embodiment of thelight-converting diffusive layer of FIG. 10;

FIG. 17 is a cross-sectional view illustrating another embodiment of anLCD device;

FIG. 18 is a cross-sectional view illustrating another embodiment of anLCD device;

FIG. 19 is a cross-sectional view illustrating another embodiment of anLCD device;

FIG. 20 is a cross-sectional view illustrating another embodiment of anLCD device;

FIG. 21 is a cross-sectional view illustrating another embodiment of anLCD device;

FIG. 22 is a cross-sectional view illustrating another embodiment of anLCD device; and

FIG. 23 is a cross-sectional view illustrating another embodiment of anLCD device.

DETAILED DESCRIPTION

It will be understood that when an element or layer is referred to asbeing “on” or “coupled to” another element or layer, the element orlayer can be directly on or connected to another element or layer orintervening elements or layers. In contrast, when an element is referredto as being “directly on” or “directly connected to” another element orlayer, there are no intervening elements or layers present. Like numbersrefer to like elements throughout. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. Expressions such as “at least one” and “at least oneselected from,” when preceding a list of elements, modify the entirelist of elements and do not modify the individual elements of the list.

The invention will now be described more fully with reference to theaccompanying drawings, in which embodiments of the invention are shown.In the drawings, the same reference numerals denote the same elements,and sizes of thicknesses of elements may be exaggerated for clarity.

It will be understood that, although the terms first, second, third,etc., may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers and/or sections should not be limited by these terms. These termsare only used to distinguish one element, component, region, layer orsection from another region, layer or section. Thus, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the invention.

Spatially relative terms, such as “lower,” “under,” “above,” “upper” andthe like, may be used herein for ease of description to describe therelationship of one element or feature to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation, in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “lower” or “under”relative to other elements or features would then be oriented “above”relative to the other elements or features. Thus, the exemplary term“under” can encompass both an orientation of above and below. The devicemay be otherwise oriented (rotated 90 degrees or at other orientations)and the spatially relative descriptors used herein interpretedaccordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes” and/or “including,” when used in thisspecification, specify the presence of stated features, integers,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Embodiments of the invention are described herein with reference tocross-section illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of the invention. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, embodiments of the invention should not be construed aslimited to the particular shapes of regions illustrated herein but areto include deviations in shapes that result, for example, frommanufacturing.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Hereinafter, the invention will be described in detail with reference tothe accompanying drawings.

Backlight units may include three color light emitting diodes (“LEDs”)as light sources. Backlight units using three color LEDs as lightsources may be applied to high quality display devices because thebacklight units using three color LEDs may obtain high color purity.However, backlight units using three color LEDs as light sources areundesirably more expensive than backlight units using cold cathodefluorescent lamps (“CCFLs”) as light sources.

In order to reduce costs, white LEDs that convert light output from anLED chip of one color into white light and output the white light havebeen developed. However, although such white LEDs may reduce costs, thewhite LEDs have lower color purity and lower color reproducibility thanthree color LEDs. Accordingly, there remains a need for a backlight unitwith improved color reproducibility and color purity, and costcompetitiveness.

FIG. 1 is a cross-sectional view illustrating an embodiment of a liquidcrystal display (“LCD”) device.

Referring to FIG. 1, the LCD device includes a backlight unit 100, and aliquid crystal panel 500 that forms an image of a specific color byusing white light emitted from the backlight unit 100. The backlightunit 100 includes a LED light source 110, and a light converting layer130. The light converting layer 130 converts light emitted from the LEDlight source 110 into white light and outputs the white light to theliquid crystal panel 500. The LED light source 110 may include asubstrate 111, and a plurality of LEDs 112 that is disposed atpredetermined intervals on the substrate 111. The LED light source 110may be a light source that emits blue light. However, the presentembodiment is not limited thereto, and the LED light source 110 may be alight source that emits ultraviolet light.

The light converting layer 130 is disposed between the LED light source110 and the liquid crystal panel 500, and is spaced apart from the LEDlight source 110 by a predetermined distance. Each of the LED lightsource 110 and the light converting layer 130 may have a planar sizecorresponding to the liquid crystal panel 500, such as in a plane viewof the LCD device from a viewing side and/or a rear side thereof.

The light converting layer 130 may include a transparent substrate 131,a light converting film 132 that is disposed such as by coating on thetransparent substrate 131 and includes semiconductor nanocrystals, and abarrier layer 135 that is disposed on a top surface of the lightconverting film 132 and includes a barrier material. The transparentsubstrate 131 may include, but is not limited to, a resin such aspolyethylene terephthalate (“PET”).

The light converting film 132 converts light emitted from the LED lightsource 110 into white light. The light converting film 132 may includesemiconductor nanocrystals that may obtain high color reproducibilityand high color purity. For example, the semiconductor nanocrystals mayinclude at least one selected from a Group II-VI material, a Group III-Vmaterial, and a Group IV element. The term “Group” refers to a group ofthe Periodic Table of the Elements. The Group II-VI material, and GroupIII-V material may each independently include at least one selected froma binary compound, a ternary compound, and a quaternary compound. TheGroup II-VI material may include at least one selected from HgTe, HgSe,HgS, CdTe, CdSe, CdS, ZnTe, ZnSe, ZnS, CdSeS, CdSeTe, CdSTe, ZnSeS,ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS,CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, HgZnTeS, CdZnSeS,CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, andHgZnSTe; the Group III-V material may include at least one selected fromGaN, GaP, InN, InP, InAs, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs,AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs,GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb,InAlNP, InAlNAs, InAlNSb, InAlPAs, and InAlPSb; and the Group IV elementmay include at least one selected from Si and Ge. The materials areexemplarily described as materials of the semiconductor nanocrystals,and other various semiconductor materials may be used as materials forthe semiconductor nanocrystals. The light converting film 132 may be,for example, a polymer film in which the semiconductor nanocrystals aredispersed.

The barrier layer 135 may be disposed on a top surface of the lightconverting film 132, toward the viewing side of the LCD. The barrierlayer 135 restricts penetration of moisture and/or oxygen thereto, suchthat the barrier layer 135 reduces or effectively prevents externalmoisture and/or oxygen from penetrating into the light converting film132. In detail, the light converting film 132 including thesemiconductor nanocrystals reacts with ambient oxygen or moisture whenreceiving light from the LED light source 110 and converting the light,to thereby cause a physicochemical change. Accordingly, as time passes,optical properties of the light converting film 132, for example, awavelength, a full width at half maximum, or quantum efficiency, may beundesirably changed. In order to maintain optical properties of thelight converting film 132, the barrier layer 135 is disposed on the topsurface of the light converting film 132 in FIG. 1. When the transparentsubstrate 131 includes a material into which moisture or oxygen maypenetrate, for example, PET, the barrier layer 135 may also be disposedon the bottom surface of the transparent substrate 131.

Each of moisture and oxygen transmission rates of the barrier layer 135may be equal to or less than, for example, about 0.1 cubic centimeterper square meter per day (cc/m²/day). However, the present embodiment isnot limited thereto, and each of the moisture and oxygen transmissionrates of the barrier layer 135 may be another value which sufficientlyrestricts the moisture and the oxygen, respectively.

The barrier material of the barrier layer 135 may include at least oneselected from an organic material and an inorganic material. The organicmaterial may include at least one selected from, for example, thiolene,hybrid epoxy, polyurea, polytetrafluoroethylene (“PTFE”),polydimethylsiloxane (“PDMS”), polyvinylchloride, polycarbonate,polystyrene, polyimide, parylene, polyethylacrylate, andpolymethylmethacrylate. The inorganic material may include at least oneselected from, for example, silicon oxide, aluminum oxide, titaniumoxide, indium oxide, tin oxide, tin indium oxide, tantalum oxide,zirconium oxide, and niobium oxide. However, the present embodiment isnot limited thereto, and any of various other organic materials orinorganic materials may be used as the barrier material. The barrierlayer 135 may have a structure in which at least one organic film and atleast one inorganic film alternate in a stack. In this case, the organicfilm may include epoxy, acrylate, or urethane other than the aboveorganic materials.

When a general or conventional backlight unit that does not include thebarrier layer 135 is driven for a long time, for example, 100 hours ormore, at a temperature higher than a room temperature, brightness ofwhite light may be reduced by 10% or more, a change (ΔC_(x), ΔC_(y)) incolor coordinates may be greater than (±0.1, ±0.1), or a change in acolor temperature may be 1000 degrees Kelvin (° K) or more. However,when the backlight unit 100 including the barrier layer 135 whosemoisture transmission rate and oxygen transmission rates are each equalto or less than about 0.1 cc/m²/day is driven for a long time, forexample, 100 hours or more, at a temperature higher than a roomtemperature, brightness of white light may be maintained, a change(ΔC_(x), ΔC_(y)) in color coordinates may be less than (±0.1, ±0.1),and/or a change in a color temperature may be 1000° K or less.Accordingly, even after a relatively long operation, since brightnessand color coordinates are not greatly changed, the backlight unit 100may ensure high reliability.

An adhesive layer (not shown) including the barrier material may befurther disposed on a side surface of the light converting layer 130.The adhesive layer may surround side surface of the light convertinglayer 130. Due to the adhesive layer, edge portions of layersconstituting the light converting layer 130 may be considered laminated.

The barrier material included in the adhesive layer reduces oreffectively prevents external moisture and/or oxygen from penetratinginto the side surface of the light converting layer 130. The adhesivelayer may have an uneven (e.g., non-uniform thickness) structurecorresponding to the edge portions of the layers constituting the lightconverting layer 130, or a multi-layer structure which is disposed on afilm. The barrier material may include at least one selected from anorganic material and an inorganic material. As described above, theorganic material may include at least one selected from, for example,thiolene, hybrid epoxy, polyurea, PTFE, PDMS, polyvinylchloride,polycarbonate, polystyrene, polyimide, parylene, polyethylacrylate, andpolymethylmethacrylate. The inorganic material may include at least oneselected from, for example, silicon oxide, aluminum oxide, titaniumoxide, indium oxide, tin oxide, tin indium oxide, tantalum oxide,zirconium oxide, and niobium oxide.

FIG. 2 is a cross-sectional view illustrating another embodiment of thelight converting layer 130 of FIG. 1. Referring to FIG. 2, a lightconverting layer 130 a may include a transparent substrate 131 a, alight converting film 132 a that is coated on the transparent substrate131 a and includes semiconductor nanocrystals, and a barrier layer 135 athat is disposed on an upper surface of the light converting film 132 aand includes a barrier material. The transparent substrate 131 a may bea substrate that may reduce or effectively prevent penetration ofexternal moisture or oxygen thereto, such as a glass substrate. In thiscase, the barrier layer 135 a may not be disposed on a bottom surface ofthe transparent substrate 131 a.

FIG. 3 is a cross-sectional view illustrating another embodiment of thelight converting layer 130 of FIG. 1. Referring to FIG. 3, a lightconverting layer 130 b may include a light converting film 132 b thatincludes semiconductor nanocrystals, and a barrier layer 135 b that isdisposed on a surface of the light converting film 132 b. In this case,the light converting layer 130 b may not include the transparentsubstrate 131 of FIG. 1. The barrier layer 135 b may be disposed on oneor both of the upper and lower surfaces of the light converting film 132b.

FIG. 5 is a cross-sectional view illustrating another embodiment of thelight converting layer 130 of FIG. 1. Referring to FIG. 5, a lightconverting layer 130 f may include a light converting film 132 f thatincludes semiconductor nanocrystals and a barrier material. The lightconverting film 132 f may be a single-layer film including both thesemiconductor nanocrystals and the barrier material. The lightconverting film 132 f of FIG. 5 converts incident light into whitelight, and reduces or effectively prevents penetration of externalmoisture and oxygen thereto. Each of moisture and oxygen transmissionrates of the light converting film 132 f may be equal to or less than,for example, about 0.1 cc/m²/day.

FIG. 6 is a cross-sectional view illustrating another embodiment of thelight converting layer 130 of FIG. 1. Referring to FIG. 6, a lightconverting layer 130 g may include a transparent substrate 131 g, and alight converting film 132 g that is disposed on the transparentsubstrate 131 g and includes semiconductor nanocrystals and a barriermaterial.

FIG. 7 is a cross-sectional view illustrating another embodiment of thelight converting layer 130 of FIG. 1. Referring to FIG. 7, a lightconverting layer 130 h may include a light converting film 132 h thatincludes semiconductor nanocrystals and a barrier material, and abarrier layer 135 h on a surface of the light converting film 132 h andincludes a barrier material. The barrier layer 135 h may be disposed onone or both of the upper and lower surfaces of the light converting film132 h. The barrier layer 135 h may reduce or effectively preventpenetration of moisture or oxygen, and the light converting film 132 hmay reduce or effectively prevent penetration of the remaining one ofmoisture and oxygen.

Also, the aforesaid adhesive layer (not shown) may be further disposedon a side surface of each of the above light converting layers.

FIG. 8 is a cross-sectional view illustrating another embodiment of thelight converting layer 130 of FIG. 1. Referring to FIG. 8, the LCDdevice may include a plurality of light converting layers sequentiallydisposed in a direction away from the LED light source 110. Theplurality of light converting layers may collectively form a lightconverting member of the LCD device. In detail, first and second lightconverting layers 130 d and 130 e are sequentially disposed in adirection away from the LED light source 110.

The first light converting layer 130 d may include a first lightconverting film 132 d, and a first barrier layer 135 d that is disposedon one or more surface of the first light converting film 132 d. Thesecond light converting layer 130 e may include a second lightconverting film 132 e, and a second barrier layer 135 e that is disposedon one or more surface of the second light converting film 132 e.

The first light converting layer 130 d and the second light convertinglayer 130 e may be spaced apart from each other in a cross-sectiondirection, and a blank layer 136 may be defined between the first lightconverting layer 130 d and the second light converting layer 130 e. Thefirst and second light converting layers 130 d and 130 e may be disposedto have an emission wavelength with higher energy (that is, a shorterwavelength) as a distance from the LED light source 110 towards theviewing side of the LCD device increases. In one embodiment, forexample, when the LED light source 110 is a blue LED light source, thefirst and second light converting layers 130 d and 130 e that aresequentially disposed in a direction away from the LED light source 110may be a red light converting layer and a green light converting layer,respectively.

Alternatively, the LCD device or a light converting member may includethree or more sequential light converting layers. The three or moresequential light converting layers may have any of the followingarrangement structures. In alternative embodiments, for example, thelight converting layers may have an arrangement structure of the LEDlight source 110-red light converting layer-green light convertinglayer-red light converting layer-green light converting layer, anarrangement structure of the LED light source 110-green light convertinglayer-red light converting layer-green light converting layer-red lightconverting layer, an arrangement structure of the LED light source110-red light converting layer-orange light converting layer-yellowlight converting layer-green light converting layer, or an arrangementstructure of the LED light source 110-red+yellow light convertinglayer-green+orange light converting layer. The arrangement structures ofthe three or more sequential light converting layers described above areexemplary and the three or more sequential light converting layers mayhave any of various other arrangement structures.

Referring back to FIG. 1, when light emitted from the LED light source110 passes through the light converting film 132 including thesemiconductor nanocrystals, white light which is a mixture of bluelight, green light and red light may be obtained. When compositionsand/or sizes of the semiconductor nanocrystals included in the lightconverting film 132 are changed, blue light, green light and red lightmay be adjusted at a desired ratio, and thus white light having highcolor reproducibility and high color purity may be obtained.

A light guide plate 120 may be further disposed between the LED lightsource 110 and the light converting layer 130. The light guide plate 120uniformly guides light output from the LED light source 110 toward thelight converting layer 130. The light guide plate 120 may include anupper surface as a light emitting surface, a lower surface as a lightincident surface, and a plurality of side surfaces connecting the upperand lower surfaces to each other. The surface of the light guide plate120 which faces the LED light source 110 may be a light incident surfaceof the light guide plate 120. A diffusive plate 140 may be furtherdisposed between the light converting layer 130 and the liquid crystalpanel 500. The diffusive plate 140 diffuses white light incident fromthe light converting layer 130 and outputs the white light. Accordingly,uniformity of the white light passing through the diffusive plate 140may be improved.

Although the diffusive plate 140 and the light converting layer 130 arespaced apart from each other in FIG. 1, the light converting layer 130may contact a bottom surface of the diffusive plate 140 as shown in FIG.4. In this case, a light converting layer 130 c may include a lightconverting film 132 c that is disposed on the bottom surface of thediffusive plate 140 and includes semiconductor nanocrystals, and abarrier layer 135 c that is disposed on a bottom surface of the lightconverting film 132 c and includes a barrier material.

A predetermined optical sheet 150 for improving optical properties suchas brightness may be further disposed between the diffusive plate 140and the liquid crystal panel 500. The optical sheet 150 may include atleast one selected from, for example, a prism sheet, a brightnessenhancement sheet and a micro-lens sheet. However, the presentembodiment is not limited thereto, and the optical sheet 150 may includeany number of sheets having various other functions. Alternatively, theoptical sheet 150 may be disposed between the LED light source 110 andthe light converting layer 130.

White light emitted from the backlight unit 100 is incident on theliquid crystal panel 500. The liquid crystal panel 500 forms an image ofa predetermined color by using the white light incident from thebacklight unit 100. The liquid crystal panel 500 may have a structure inwhich a first polarization plate 510, a liquid crystal layer 520, asecond polarization plate 530, and a color filter 540 are sequentiallydisposed. White light emitted from the backlight unit 100 transmitsthrough the first polarization plate 510, the liquid crystal layer 520and the second polarization plate 530 and then is incident on the colorfilter 540 to form the image of the predetermined color.

Since the light converting film 132 of the light converting layer 130includes the semiconductor nanocrystals, the backlight unit 110constructed as described above may improve color reproducibility andcolor purity. Since the light converting film 132 is spaced apart fromthe LED light source 110, deterioration of the semiconductornanocrystals due to heat generated from the LEDs 112 is reduced oreffectively prevented. Also, since the barrier layer 135 is disposed onthe light converting film 132, penetration of external moisture andoxygen into the light converting film 132 may be reduced or effectivelyprevented. Accordingly, when the light converting film 132 convertslight incident from the LED light source 110 into white light, opticalproperties such as a wavelength, a full width at half maximum andquantum efficiency may not be changed, and thus brightness and colorcoordinates of the backlight unit 100 may be maintained even when thebacklight unit 100 is driven for a long time.

FIG. 9 is a cross-sectional view illustrating another embodiment of anLCD device. The following explanation will focus on a difference fromthe previous embodiment.

Referring to FIG. 9, a backlight unit 200 includes an LED light source210, and a light converting layer 230. The light converting layer 230converts light incident from the LED light source 210 into white lightand outputs the white light to the liquid crystal panel 500. The lightconverting layer 230 is disposed between the LED light source 210 andthe liquid crystal panel 500, and is spaced apart from the LED lightsource 210. The LED light source 210 may be a light source that emitsblue light, or the LED light source 210 may be a light source that emitsultraviolet light. The LED light source 210 may include a substrate 211,and a plurality of LEDs 212 that is disposed at predetermined intervalson the substrate 211.

The light converting layer 230 may include a transparent substrate 231,a light converting film 232 that is disposed such as by coating on thetransparent substrate 231 and includes semiconductor nanocrystals, and abarrier layer 235 that is disposed on a top surface of the lightconverting film 232 and includes a barrier material. The transparentsubstrate 231 may include, but is not limited to, a resin such as PET.The barrier layer 235 reduces or effectively prevents external moistureand/or oxygen from penetrating into the light converting film 232 asdescribed above. When the transparent substrate 231 includes a materialinto which moisture or oxygen may penetrate such as PET, the barrierlayer 235 may also be disposed on the bottom surface of the transparentsubstrate 231.

Each of moisture and oxygen transmission rates of the barrier layer 235may be, but is not limited to, equal to or less than about 0.1cc/m²/day. The barrier material of the barrier layer 235 may include atleast one selected from an organic material and an inorganic material.The organic material may include at least one selected from, forexample, thiolene, hybrid epoxy, polyurea, PTFE, PDMS,polyvinylchloride, polycarbonate, polystyrene, polyimide, parylene,polyethylacrylate, and polymethylmethacrylate. The inorganic materialmay include at least one selected from, for example, silicon oxide,aluminum oxide, titanium oxide, indium oxide, tin oxide, tin indiumoxide, tantalum oxide, zirconium oxide, and niobium oxide. However, thepresent embodiment is not limited thereto, and any of various otherorganic materials or inorganic materials may be used as the barriermaterial. The barrier layer 235 may have a structure in which at leastone organic film and at least one inorganic film alternate in a stack.

Alternatively, any of the light converting layers shown in FIGS. 2, 3and 5-7 may be used as the light converting layer 230 shown in FIG. 9.As shown in FIG. 2, the light converting layer 130 a as the lightconverting layer 230 may include the transparent substrate 131 a, thelight converting film 132 a that is coated on the transparent substrate131 a and includes semiconductor nanocrystals, and the barrier layer 135a that is disposed on the light converting film 132 a. In this case,since the transparent substrate 131 a is a substrate that may reduce oreffectively prevent penetration of external moisture or oxygen, thebarrier layer 135 a may be disposed on only a top surface of the lightconverting film 132 a.

As shown in FIG. 3, the light converting layer 130 b as the lightconverting layer 230 may include the light converting film 132 b thatincludes semiconductor nanocrystals, and the barrier layer 135 b that isdisposed on one or more surface of the light converting film 132 b. Asshown in FIG. 5, the light converting layer 130 f as the lightconverting layer 230 may convert incident light into white light, andmay reduce or effectively prevent penetration of external moisture andoxygen thereto. Each of moisture and oxygen transmission rates of thelight converting film 132 f may be equal to or less than, for example,about 0.1 cc/m²/day. As shown in FIG. 6, the light converting layer 130g as the light converting layer 230 may include the transparentsubstrate 131 g, and the light converting film 132 g that is disposed onthe transparent substrate 131 g and includes semiconductor nanocrystalsand a barrier material. As shown in FIG. 7, the light converting layer130 h as the light converting layer 230 may include a light convertingfilm 132 h that includes semiconductor nanocrystals and a barriermaterial, and the barrier layer 135 h that is disposed on one or moresurface of the light converting film 132 h and includes a barriermaterial. The barrier layer 135 h may reduce or effectively preventpenetration of moisture or oxygen thereto, and the light converting film132 h may reduce or effectively prevent penetration of the remaining oneof moisture and oxygen.

Alternatively, the LCD device shown in FIG. 9 may further include aplurality of light converting layers sequentially disposed in adirection away from the LED light source 210, for example, as shown inFIG. 8. The plurality of light converting layers may be spaced apartfrom one another, and a blank layer may be defined between the lightconverting layers. The plurality of light converting layers may bedisposed to have an emission wavelength with higher energy (that is, ashorter wavelength) as a distance from the LED light source 210increases. Arrangement structures of the plurality of light convertinglayers may be variously modified as described above.

An adhesive layer (not shown) including the barrier material may befurther disposed on a side surface of the light converting layer 230.The adhesive layer may surround the side surface of the light convertinglayer 230. Due to the adhesive layer, edge portions of layersconstituting the light converting layer 230 may be considered laminated.A barrier material included in the adhesive layer reduces or effectivelyprevents external moisture and/or oxygen from penetrating into the sidesurface of the light converting layer 230. The adhesive layer may havean uneven structure corresponding to the edge portions of the layersconstituting the light converting layer 230, or a multi-layer structuredisposed on a film.

A diffusive plate 240 is disposed between the LED light source 210 andthe light converting layer 230. When light emitted from the LED lightsource 210 transmits through the diffusive plate 240, uniformity of thelight may be improved. The light passing through the diffusive plate 240is incident on the light converting layer 230 and is converted intowhite light. Although the diffusive plate 240 and the light convertinglayer 230 are spaced apart from each other in FIG. 9, the lightconverting layer 230 may contact a top surface of the diffusive plate240.

A light guide plate 220 may be further disposed between the LED lightsource 210 and the diffusive plate 240.

A predetermined optical sheet 250 for improving optical properties suchas brightness may be further disposed between the light converting layer230 and the liquid crystal panel 500. Alternatively, the optical sheet250 may be disposed between the LED light source 210 and the lightconverting layer 230.

FIG. 10 is a cross-sectional view illustrating another embodiment of anLCD device. The following explanation will focus on a difference fromthe previous embodiments.

Referring to FIG. 10, the LCD device includes a backlight unit 300, anda liquid crystal panel 500 that forms an image of a predetermined colorby using white light emitted from the backlight unit 300. The backlightunit 300 includes an LED light source 310, and a light converting layer330 that is spaced apart from the LED light source 310. The LED lightsource 310 may include a substrate 311, and a plurality of LEDs 312 thatis disposed at predetermined intervals on the substrate 311. The LEDlight source 310 may be a light source that emits blue light, or a lightsource that emits ultraviolet light.

The light converting layer 330 includes a light-converting diffusivefilm 332 that includes semiconductor nanocrystals for convertingincident light into white light and light diffusing particles fordiffusing incident light, and a barrier layer 335 that is disposed onone or more surface of the light-converting diffusive film 332. Each ofthe LED light source 310 and the light converting layer 330 may have aplanar size corresponding to the liquid crystal panel 500.

The light-converting diffusive film 332 may perform both a lightconversion function and a light diffusion function. The semiconductornanocrystals may include at least one selected from a Group II-VImaterial, a Group III-V material, and a Group IV element. As is furtherdisclosed above, the Group II-VI material may include at least oneselected from HgTe, HgSe, HgS, CdTe, CdSe, Cds, ZnTe, ZnSe, and ZnS, theGroup III-V material may include at least one selected from GaN, GaP,InN, InP, and InAs, and the Group IV element may include at least oneselected from Si and Ge. The materials are exemplarily described asmaterials of the semiconductor nanocrystals, and other varioussemiconductor materials may be used as materials for the semiconductornanocrystals.

The barrier layer 335 reduces or effectively prevents external moistureand/or oxygen from penetrating into the light-converting diffusive film332. Each of moisture and oxygen transmission rates of the barrier layer335 may be, but is not limited to, equal to or less than about 0.1cc/m²/day.

A barrier material of the barrier layer 335 may include at least oneselected from an organic material and an inorganic material. The barrierlayer 335 may have a multi-layer structure in which at least one organicfilm and at least one inorganic film alternate in a stack. An adhesivelayer (not shown) including the barrier material may be further disposedon a side surface of the light converting layer 330. The adhesive layermay surround the side surface of the light converting layer 330. Due tothe adhesive layer, edge portions of layers constituting the lightconverting layer 330 may be considered laminated.

FIG. 11 is a cross-sectional view illustrating another embodiment of thelight converting layer 330 of FIG. 10. Referring to FIG. 11, a lightconverting layer 330 a may include a transparent substrate 331 a, alight-converting diffusive film 332 a that is coated on the transparentsubstrate 331 a and includes semiconductor nanocrystals and lightdiffusing particles, and a barrier layer 335 a that is disposed on a topsurface of the light-converting diffusive film 332 a. When thetransparent substrate 331 a includes a material into which moisture oroxygen may penetrate such as PET, the barrier layer 335 a may also bedisposed on the bottom surface of the transparent substrate 331 a.

FIG. 12 is a cross-sectional view illustrating another embodiment of thelight converting layer 330 of FIG. 10. Referring to FIG. 12, a lightconverting layer 330 b may include a transparent substrate 331 b, alight-converting diffusive film 332 b that is coated on the transparentsubstrate 331 b and includes semiconductor nanocrystals and lightdiffusing particles, and a barrier layer 335 b that is disposed on a topsurface of the light-converting diffusive film 332 b. The transparentsubstrate 331 b may be a substrate that reduces or effectively preventspenetration of external moisture or oxygen such as a glass substrate. Inthis case, the barrier layer 335 b may be disposed on only the topsurface of the light-converting diffusive film 332 b.

FIG. 13 is a cross-sectional view illustrating another embodiment of thelight converting layer 330 of FIG. 10. Referring to FIG. 13, a lightconverting layer 330 e may include a light-converting diffusive film 332e that includes semiconductor nanocrystals for converting incident lightinto white light, light diffusing particles for diffusing incidentlight, and a barrier material for reducing or effectively preventingpenetration of external moisture and/or oxygen thereto. Thelight-converting diffusive film 332 e may be a single-layer filmincluding the semiconductor nanocrystals, the light diffusing particlesand the barrier material.

FIG. 14 is a cross-sectional view illustrating another embodiment of thelight converting layer 330 of FIG. 10. Referring to FIG. 14, a lightconverting layer 330 f may include a transparent substrate 331 f, and alight-converting diffusive film 332 f that is disposed on thetransparent substrate 331 f and includes semiconductor nanocrystals,light diffusing particles and a barrier material.

FIG. 15 is a cross-sectional view illustrating another embodiment of thelight converting layer 330 of FIG. 10. Referring to FIG. 15, a lightconverting layer 330 g may include a light-converting diffusive film 332g that includes semiconductor nanocrystals, light diffusing particlesand a barrier material, and a barrier layer 335 g that is disposed onone or more surface of the light-converting diffusive film 332 g andincludes a barrier material. In this case, the barrier layer 335 g mayreduce or effectively prevent penetration of moisture or oxygen, and thelight-converting diffusive film 332 g may reduce or effectively preventpenetration of the remaining one of moisture and oxygen.

FIG. 16 is a cross-sectional view illustrating another embodiment of thelight converting layer 330 of FIG. 10. Referring to FIG. 16, the LCDdevice may include a plurality of light converting layers sequentiallydisposed in a direction away from the LED light source 310. In detail,first and second light converting layers 330 c and 330 d aresequentially disposed in a direction away from the LED light source 310.

The first light converting layer 330 c may include a firstlight-converting diffusive film 332 c, and a first barrier layer 335 cthat is disposed on one or more surface of the first light-convertingdiffusive film 332 c. The second light converting layer 330 d mayinclude a second light-converting diffusive film 332 d, and a secondbarrier layer 335 d that is disposed on one or more surface of thesecond light-converting diffusive film 332 d.

The first light converting layer 330 c and the second light convertinglayer 330 d may be spaced apart from each other, and a blank layer 336may be defined between the first light converting layer 330 c and thesecond light converting layer 330 d. The first and second lightconverting layers 330 c and 330 d may be disposed to have an emissionwavelength with higher energy (that is, a shorter wavelength) as adistance from the LED light source 310 increases. In one embodiment, forexample, when the LED light source 310 is a blue LED light source, thefirst and second light converting layers 330 c and 330 d which aresequentially disposed in a direction away from the LED light source 310may be a red light converting layer and a green light converting layer,respectively.

Alternatively, the LCD device or a light converting member of the LCDdevice may include three or more sequential light converting layers. Thethree or more light converting layers may have any of the followingarrangement structures. In alternative embodiments, for example, thelight converting layers may have an arrangement structure of the LEDlight source 310-red light converting layer-green light convertinglayer-red light converting layer-green light converting layer, anarrangement structure of the LED light source 310-green light convertinglayer-red light converting layer-green light converting layer-red lightconverting layer, an arrangement structure of the LED light source310-red light converting layer-orange light converting layer-yellowlight converting layer-green light converting layer, or an arrangementstructure of the LED light source 310-red+yellow light convertinglayer-green+orange light converting layer. The aforesaid arrangementstructures of the three or more sequential light converting layers areexemplary, and the three or more sequential light converting layers mayhave any of various other arrangement structures.

Referring back to FIG. 10, when light emitted from the LED light source310 passes through the light-converting diffusive film 332 that includesthe semiconductor nanocrystals and the light diffusing particles, whitelight that is a mixture of blue light, green light and red light may beobtained. When compositions and/or sizes of the semiconductornanocrystals included in the light-converting diffusive film 332 arechanged, the blue light, the green light and the red light may beadjusted at a desired ratio, and thus white light having high colorreproducibility and high color purity may be obtained.

A light guide plate 320 may be further disposed between the LED lightsource 310 and the light converting layer 330. The light guide plate 320uniformly guides light output from the LED light source 310 toward thelight converting layer 330.

A predetermined optical sheet 350 for improving optical properties suchas brightness may be further disposed between the light converting layer330 and the liquid crystal panel 500. The optical sheet 350 may include,but is not limited to, at least one selected from, for example, a prismsheet, a brightness enhancement sheet and a micro-lens sheet.Alternatively, the optical sheet 350 may be disposed between the LEDlight source 310 and the light converting layer 330.

White light emitted from the backlight unit 300 is incident on theliquid crystal panel 500. The liquid crystal panel 500 forms an image ofa predetermined color by using the white light incident from thebacklight unit 300. The liquid crystal panel 500 may have a structure inwhich a first polarization plate 510, a liquid crystal layer 520, asecond polarization plate 530 and a color filter 540 are sequentiallydisposed. The white light emitted from the backlight unit 300 transmitsthrough the first polarization plate 510, the liquid crystal layer 520and the second polarization plate 530, and then is incident on the colorfilter 540, to form the image of the predetermined color.

FIG. 17 is a cross-sectional view illustrating another embodiment of anLCD device. The following explanation will focus on a difference fromthe previous embodiments.

Referring to FIG. 17, the LCD device includes a backlight unit 800, andthe liquid crystal panel 500 that forms an image of a predeterminedcolor by using white light emitted from the backlight unit 800. Thebacklight unit 800 includes an LED light source 810, a light guide plate820 that is disposed between the LED light source 810 and the liquidcrystal panel 500, and a barrier layer 835 that is disposed on one ormore surface of the light guide plate 820.

The LED light source 810 may include a substrate 811, and a plurality ofLEDs 812 that is disposed at predetermined intervals on the substrate811. The LED light source 810 may be a light source that emits bluelight, or a light source that emits ultraviolet light.

The light guide plate 820 that guides light incident from the LED lightsource 810 toward the liquid crystal panel 500 may include semiconductornanocrystals. Accordingly, the light guide plate 820 converts incidentlight into white light and guides the white light toward the liquidcrystal panel 500. The barrier layer 835 is disposed on one or moresurface of the light guide plate 820, and reduces or effectivelyprevents external moisture and/or oxygen from penetrating into the lightguide plate 820. Each of moisture and oxygen transmission rates of thebarrier layer 835 may be equal to or less than, for example, about 0.1cc/m²/day. However, the present embodiment is not limited thereto, andeach of moisture and oxygen transmission rates of the barrier layer 835may be another value which sufficiently restricts the moisture and theoxygen, respectively.

A barrier material of the barrier layer 835 may include at least oneselected from an organic material and an inorganic material. The organicmaterial may include at least one selected from, for example, thiolene,hybrid epoxy, polyurea, PTFE, PDMS, polyvinylchloride, polycarbonate,polystyrene, polyimide, parylene, polyethylacrylate, andpolymethylmethacrylate. The inorganic material may include at least oneselected from, for example, silicon oxide, aluminum oxide, titaniumoxide, indium oxide, tin oxide, tin indium oxide, tantalum oxide,zirconium oxide, and niobium oxide. However, the present embodiment isnot limited thereto, and any of various other organic materials orinorganic materials may be used as the barrier material. The barrierlayer 835 may have a structure in which at least one organic film and atleast one inorganic film alternate in a stack.

An adhesive layer (not shown) including the barrier material may befurther disposed on a side surface of the light guide plate 820. Theadhesive layer may surround the side surface of the light guide plate820. The barrier material included in the adhesive layer reduces oreffectively prevents external moisture and/or oxygen from penetratinginto the side surface of the light guide plate 820. The barrier materialmay include at least one selected from an organic material and aninorganic material.

A diffusive plate 840 may be further disposed between the light guideplate 820 and the liquid crystal panel 500. Since the diffusive plate840 diffuses white light incident from the light guide plate 820 andoutputs the white light, uniformity of the white light passing throughthe diffusive plate 840 may be improved.

A predetermined optical sheet 850 for improving optical properties suchas brightness may be further disposed between the diffusive plate 840and the liquid crystal panel 500. The optical sheet 850 may include, butis not limited to, at least one selected from a prism sheet, abrightness enhancement sheet or a micro-lens sheet.

FIG. 18 is a cross-sectional view illustrating another embodiment of anLCD device. The following explanation will focus on a difference fromthe previous embodiments.

Referring to FIG. 18, the LCD device includes a backlight unit 900, anda liquid crystal panel 500 that forms an image of a predetermined colorby using white light emitted from the backlight unit 900. The backlightunit 900 includes an LED light source 910, a light guide plate 920 thatis disposed between the LED light source 910 and the liquid crystalpanel 500, and a barrier layer 935 that is disposed on one or moresurface of the light guide plate 920.

The LED light source 910 may include a substrate 911, and a plurality ofLEDs 912 that is disposed at predetermined intervals on the substrate911. The LED light source 910 may be a light source that emits bluelight, or a light source that emits ultraviolet light.

The light guide plate 920 that guides light incident from the LED lightsource 910 toward the liquid crystal panel 500 may include semiconductornanocrystals and light diffusing particles. Accordingly, the light guideplate 920 may convert incident light into white light, diffuse the whitelight and guide the diffused white light toward the liquid crystal panel500.

An adhesive layer (not shown) including a barrier material may befurther disposed on a side surface of the light guide plate 920.

A predetermined optical sheet 950 for improving optical properties suchas brightness may be further disposed between the light guide plate 920and the liquid crystal panel 500. The optical sheet 950 may include, butis not limited to, at least one selected from a prism sheet, abrightness enhancement sheet or a micro-lens sheet.

FIG. 19 is a cross-sectional view illustrating another embodiment of anLCD device.

Referring to FIG. 19, the LCD device includes a backlight unit 400, andthe liquid crystal panel 500 that forms an image of a predeterminedcolor by using white light emitted from the backlight unit 400. Thebacklight unit 400 includes an LED light source 410, a light guide plate420 that uniformly guides light emitted from the LED light source 410toward the liquid crystal panel 500, and a light converting layer 430that converts light emitted from the light guide plate 420 into whitelight.

The LED light source 410 may be disposed on one or more side of thelight guide plate 420. The light guide plate 420 may include an uppersurface as a light emitting surface, a lower surface as a reartransmitting or reflecting surface, and a plurality of side surfacesconnecting the upper and lower surfaces to each other. One more of theside surfaces which faces the LED light source 410 may be a lightincident surface of the light guide plate 420.

The LED light source 410 may include a substrate 411, and a plurality ofLEDs 412 that is disposed at predetermined intervals on the substrate411. The LED light source 410 may be a light source that emits bluelight, or a light source that emits ultraviolet light. A reflectiveplate 415 for reflecting light output from the light guide plate 420 tothe liquid crystal panel 500 may be further disposed under the lightguide plate 420.

The light converting layer 430 converts light incident from the lightguide plate 420 into white light, and emits the white light to theliquid crystal panel 500. The light converting layer 430 may have aplanar size corresponding to the liquid crystal panel 500. The lightconverting layer 430 may include a transparent substrate 431, a lightconverting film 432 that is disposed such as by coating on thetransparent substrate 431 and includes semiconductor nanocrystals, and abarrier layer 435 that is disposed on a top surface of the lightconverting film 432 and includes a barrier material.

The light converting film 432 may include semiconductor nanocrystalsthat may ensure high color reproducibility and high color purity. Thelight converting film 432 may be, for example, a polymer film in whichthe semiconductor nanocrystals are dispersed. The barrier layer 435 maybe disposed on the top surface of the light converting film 432. Thebarrier layer 435 reduces or effectively prevents external moistureand/or oxygen from penetrating into the light converting film 432. Whenthe transparent substrate 431 includes of a material in which moistureor oxygen may penetrate such as PET, the barrier layer 435 may also bedisposed on the bottom surface of the transparent substrate 431.

Each of moisture and oxygen transmission rates of the barrier layer 435may be equal to or less than, for example, about 0.1 cc/m²/day. Thepresent embodiment is not limited thereto, and each of moisture andoxygen transmission rates of the barrier layer 435 may be another valuewhich sufficiently restricts the moisture and the oxygen, respectively.

The barrier material of the barrier layer 435 may include at least oneselected from an organic material and an inorganic material. The organicmaterial may include at least one selected from, for example, thiolene,hybrid epoxy, polyurea, PTFE, PDMS, polyvinylchloride, polycarbonate,polystyrene, polyimide, parylene, polyethylacrylate, andpolymethylmethacrylate. The inorganic material may include at least oneselected from, for example, silicon oxide, aluminum oxide, titaniumoxide, indium oxide, tin oxide, tin indium oxide, tantalum oxide,zirconium oxide, and niobium oxide. However, the present embodiment isnot limited thereto, and any of various other organic materials orinorganic materials may be used as the barrier material. The barrierlayer 435 may have a structure in which at least one organic film and atleast one inorganic film alternate in a stack.

When a general or conventional backlight unit that does not include thebarrier layer 435 is driven for a long time, for example, 100 hours ormore, at a temperature higher than a room temperature, brightness ofwhite light may be reduced by 10% or more, a change (ΔC_(x), ΔC_(y)) incolor coordinates may be greater than (±0.1, ±0.1), or a change in acolor temperature may be 1000° K or more. However, when the backlightunit 400 including the barrier layer 435 whose moisture transmissionrate and oxygen transmission rates are each equal to or less than about0.1 cc/m²/day is driven for a long time, for example, 100 hours or more,at a temperature higher than a room temperature, brightness of whitelight may be maintained, a change (ΔC_(x), ΔC_(y)) in color coordinatesmay be less than (±0.1,±0.1), and/or a change in a color temperature maybe 1000° K or less.

Various modified examples of the light converting layer 430 areillustrated in FIGS. 2, 3, 5, 6 and 7, and a detailed explanationthereof has already been made and thus will not be repeated here. TheLCD device of FIG. 19 may further include a plurality of lightconverting layers sequentially disposed in a direction away from the LEDlight source 410 and/or the light guide plate 420. The light convertinglayers may be spaced apart from one another, and a blank layer may bedefined between the plurality of light converting layers. The pluralityof light converting layers may be disposed to have an emissionwavelength with higher energy (that is, a shorter wavelength) as adistance from the LED light source 410 and/or the light guide plate 420increases. Arrangement structures of the plurality of light convertinglayers may be variously modified as described above.

An adhesive layer (not shown) including the barrier material may befurther disposed on a side surface of the light converting layer 430.The adhesive layer may surround the side surface of the light convertinglayer 430. Due to the adhesive layer, edge portions of layersconstituting the light converting layer 430 may be considered laminated.The barrier material included in the adhesive layer reduces oreffectively prevents external moisture and/or oxygen from penetratinginto the side surface of the light converting layer 430. The adhesivelayer may have an uneven structure corresponding to the edge portions ofthe layers constituting the light converting layer 430, or a multi-layerstructure disposed on a film. The barrier material may include at leastone selected from an organic material and an inorganic material.

When light emitted from the LED light source 410 passes through thelight guide plate 420 and the light converting film 432, white lightthat is a mixture of blue light, green light and red light may beobtained. When compositions and/or sizes of the semiconductornanocrystals included in the light converting film 432 are changed, theblue light, the green light and the red light may be adjusted at adesired ratio, and thus white light having high color reproducibilityand high color purity may be obtained.

A diffusive plate 440 may be further disposed between the lightconverting layer 430 and the liquid crystal panel 500. The diffusiveplate 440 diffuses white light incident from the light converting layer430 and outputs the white light. Accordingly, uniformity of the whitelight passing through the diffusive plate 440 may be improved. Althoughthe diffusive plate 440 and the light converting layer 430 are spacedapart from each other in FIG. 19, the light converting layer 430 maycontact a bottom surface of the diffusive plate 440.

A predetermined optical sheet 450 for improving optical properties suchas brightness may be further disposed between the diffusive plate 440and the liquid crystal panel 500. The optical sheet 450 may include, butis not limited to, at least one selected from a prism sheet, abrightness enhancement sheet and a micro-lens sheet.

FIG. 20 is a cross-sectional view illustrating another embodiment of anLCD device. The following explanation will focus on a difference fromthe previous embodiments.

Referring to FIG. 20, the LCD device includes a backlight unit 600, anda liquid crystal panel 500 that forms an image of a predetermined colorby using white light emitted from the backlight unit 600. The backlightunit 600 includes an LED light source 610, a light guide plate 620 thatuniformly guides light emitted from the LED light source 610 toward theliquid crystal panel 500, and a light converting layer 630 that convertslight emitted from the light guide plate 620 into white light.

The LED light source 610 may be disposed on one or more side of thelight guide plate 620, and a reflective plate 615 may be furtherdisposed under the light guide plate 620. The LED light source 610 maybe a light source that emits blue light, or a light source that emitsultraviolet light. The LED light source 610 may include a substrate 611,and a plurality of LEDs 612 that is disposed at predetermined intervalson the substrate 611.

The light converting layer 630 which converts light incident from theLED light source 610 into white light is disposed between the lightguide plate 620 and the liquid crystal panel 500. The light convertinglayer 630 may include a transparent substrate 631, a light convertingfilm 632 that is coated on the transparent substrate 631 and includessemiconductor nanocrystals, and a barrier layer 635 that is disposed ona top surface of the light converting film 632. The barrier layer 635reduces or effectively prevents external moisture and/or oxygen frompenetrating into the light converting film 632. When the transparentsubstrate 631 includes a material into which moisture or oxygen maypenetrate such as PET, the barrier layer 635 may also be disposed on thebottom surface of the transparent substrate 631.

Each of moisture and oxygen transmission rates of the barrier layer 635may be, but is not limited to, equal to or less than about 0.1cc/m²/day. A barrier material of the barrier layer 635 may include atleast one selected from an organic material and an inorganic material.The barrier layer 635 may have a structure in which at least one organicfilm and at least one inorganic film alternate in a stack.

Various modified examples of the light converting layer 630 areillustrated in FIGS. 2, 3, 5, 6 and 7, and a detailed explanationthereof has already been made and thus will not be repeated here. TheLCD device of FIG. 20 may further include a plurality of lightconverting layers sequentially disposed in a direction away from the LEDlight source 610 and/or the light guide plate 620. The plurality oflight converting layers may be spaced apart from one another, and ablank layer may be defined between the plurality of light convertinglayers. The plurality of light converting layers may be disposed to havean emission wavelength with higher energy (that is, a shorterwavelength) as a distance from the LED light source 610 and/or the lightguide plate 620 increases. Arrangement structures of the plurality oflight converting layers may be variously modified as described above.

An adhesive layer (not shown) including the barrier material may befurther disposed on a side surface of the light converting layer 630.The adhesive layer may surround the side surface of the light convertinglayer 630. The barrier material may include at least one selected froman organic material and an inorganic material.

A diffusive plate 640 may be further disposed between the LED lightsource 610 and the light converting layer 630. Uniformity of lightemitted from the LED light source 610 may be improved while passingthrough the diffusive plate 640, and the light passing through thediffusive plate 640 may be incident on the light converting layer 630may be converted into white light. Although the diffusive plate 640 andthe light converting layer 630 are spaced apart from each other in FIG.12, the light converting layer 630 may contact a top surface of thediffusive plate 640.

A predetermined optical sheet 650 for improving optical properties suchas brightness may be further disposed between the light converting layer630 and the liquid crystal panel 500.

FIG. 21 is a cross-sectional view illustrating another embodiment of anLCD device. The following explanation will focus on a difference fromthe previous embodiments.

Referring to FIG. 21, the LCD device includes a backlight unit 700, andthe liquid crystal panel 500 that forms an image of a predeterminedcolor by using white light emitted from the backlight unit 700. Thebacklight unit 700 includes an LED light source 710, a light guide plate720 that uniformly guides light emitted from the LED light source 710toward the liquid crystal panel 500, and a light converting layer 730that converts light emitted from the light guide plate 720 into whitelight.

The LED light source 710 may be disposed on one or more side of thelight guide plate 720, and a reflective plate 715 may be furtherdisposed under the light guide plate 720. The LED light source 710 maybe a light source that emits blue light, or a light source that emitsultraviolet light. The LED light source 710 may include a substrate 711,and a plurality of LEDs 712 that is disposed at predetermined intervalson the substrate 711.

The light converting layer 730 is disposed between the light guide plate720 and the liquid crystal panel 500. The light converting layer 730includes a diffusive film 732 that includes semiconductor nanocrystalsfor converting incident light into white light and light diffusingparticles for diffusing incident light, and a barrier layer 735 that isdisposed on one or more surface of the light-converting diffusive film732. The light-converting diffusive film 732 may convert light intowhite light and diffuse light.

Each of moisture and oxygen transmission rates of the barrier layers 735may be, but is not limited to, equal to or less than about 0.1cc/m²/day.

Various modified examples of the light converting layer 730 areillustrated in FIGS. 11 through 15, and a detailed explanation thereofhas already been made and thus will not be repeated here. The LCD deviceof FIG. 21 may include a plurality of light converting layerssequentially disposed in a direction away from the LED light source 710and/or the light guide plate 720. The plurality of light convertinglayers may be spaced apart from one another, and a blank layer may bedefined between the plurality of light converting layers. The pluralityof light converting layers may be disposed to have an emissionwavelength with higher energy (that is, a shorter wavelength) as adistance from the LED light source 710 and/or the light guide plate 720increases. Arrangement structures of the plurality of light convertinglayers may be variously modified as described above.

A predetermined optical sheet 750 for improving optical properties suchas brightness may be further disposed between the light converting layer730 and the liquid crystal panel 500.

An adhesive layer (not shown) including the barrier material may befurther formed on a side surface of the light converting layer 730. Theadhesive layer may surround the side surface of the light convertinglayer 730.

FIG. 22 is a cross-sectional view illustrating another embodiment of anLCD device. The following explanation will focus on a difference fromthe previous embodiments.

Referring to FIG. 22, the LCD device includes a backlight unit 1100, andthe liquid crystal panel 500 that forms an image of a predeterminedcolor by using white light emitted from the backlight unit 1100. Thebacklight unit 1100 includes an LED light source 1110, and a light guideplate 1120 that uniformly guides light emitted from the LED light source1110 toward the liquid crystal panel 500.

The LED light source 1110 may be disposed on one or more side of thelight guide plate 1120, and a reflective plate 1115 may be furtherdisposed under the light guide plate 1120. The LED light source 1110 maybe a light source that emits blue light, or a light source that emitsultraviolet light. The LED light source 1110 may include a substrate1111, and a plurality of LEDs 1112 that is disposed at predeterminedintervals on the substrate 1111.

The light guide plate 1120 for guiding light incident from the LED lightsource 1110 toward the liquid crystal panel 500 may includesemiconductor nanocrystals. Accordingly, the light guide plate 1120 mayconvert incident light into white light, and may guide light toward theliquid crystal panel 500. A barrier layer 1135 is disposed on one ormore surface of the light guide plate 1120, and reduces or effectivelyprevents external moisture and/or oxygen from penetrating into the lightguide plate 1120.

A diffusive plate 1140 may be further disposed between the light guideplate 1120 and the liquid crystal panel 500. The diffusive plate 11440may diffuse white light incident from the light guide plate 1120 andoutputs the diffused white light. Accordingly, uniformity of the whitelight passing through the diffusive plate 1140 may be improved.

A predetermined optical sheet 1150 for improving optical properties suchas brightness may be further disposed between the diffused plate 1140and the liquid crystal panel 500. The optical sheet 1150 may include atleast one selected from, for example, a prism sheet, a brightnessenhancement sheet and a micro-lens sheet.

An adhesive layer (not shown) including the barrier material may befurther disposed on a side surface of the light guide plate 1120. Theadhesive layer may surround the side surface of the light guide plate1120.

FIG. 23 is a cross-sectional view illustrating another embodiment of anLCD device. The following explanation will focus on a difference fromthe previous embodiments.

Referring to FIG. 23, the LCD device includes a backlight unit 1200, andthe liquid crystal panel 500 that forms an image of a predeterminedcolor by using white light emitted from the backlight unit 1200. Thebacklight unit 1200 includes an LED light source 1210, and a light guideplate 1220 that uniformly guides light emitted from the LED light source1210 toward the liquid crystal panel 500.

The LED light source 1210 may be disposed on one or more side of thelight guide plate 1220, and a reflective plate 1215 may be furtherdisposed under the light guide plate 1220. The LED light source 1210 maybe a light source that emits blue light, or a light source that emitsultraviolet light. The LED light source 1210 may include a substrate1211, and a plurality of LEDs 1212 that is disposed at predeterminedintervals on the substrate 1211.

The light guide plate 1220 that guides light incident from the LED lightsource 1210 toward the liquid crystal panel 500 may includesemiconductor nanocrystals for converting incident light into whitelight and light diffusing particles for diffusing incident light.Accordingly, the light guide plate 1220 may convert incident light intowhite light, diffuse the white light, and guide the diffused white lighttoward the liquid crystal panel 500. A barrier layer 1235 is disposed onone or more surface of the light guide plate 1220, and reduces oreffectively prevents external moisture and/or oxygen from penetratinginto the light guide plate 1220.

A predetermined optical sheet 1250 for improving optical properties suchas brightness may be further disposed between the light guide plate 1220and the liquid crystal panel 500. The optical sheet 1250 may include,but is not limited to, at least one selected from a prism sheet, abrightness enhancement sheet and a micro-lens sheet.

An adhesive layer (not shown) including the barrier layer may be furtherdisposed on a side surface of the light guide plate 1220. The adhesivelayer may surround the side surface of the light converting layer 1220.

According to the one or more embodiments, since a light converting layerfor converting incident light into white light includes semiconductornanocrystals, color reproducibility and color purity of white light maybe improved. Since the light converting layer including thesemiconductor nanocrystals is spaced apart from an LED light source,deterioration of the semiconductor nanocrystals due to heat generatedfrom LEDs of the light source is reduced or effectively prevented. Also,since the light converting layer includes a barrier material,penetration of external moisture or oxygen into the semiconductornanocrystals is reduced or effectively prevented. Accordingly, when thelight converting layer converts incident light into white light, opticalproperties such as a wavelength, a full width at half maximum or quantumefficiency may not be changed, and thus brightness and color coordinatesof white light may be maintained even when a backlight unit is drivenfor a long time.

While the invention has been particularly shown and described withreference to embodiments thereof, these embodiments are provided for thepurposes of illustration and it will be understood by those of ordinaryskill in the art that various modifications and equivalent otherembodiments can be made from the invention.

What is claimed is:
 1. A backlight unit for a liquid crystal displaydevice comprising a liquid crystal panel, the backlight unit comprising:a light source comprising a light-emitting diode which generates andemits light; and a light converting layer between the light source andthe liquid crystal panel, and spaced apart from the light source,wherein the light converting layer converts the light from the lightsource into another light and emits the another light toward the liquidcrystal panel, the light converting layer comprising: semiconductornanocrystals, and a barrier material which restricts penetration ofmoisture or oxygen, wherein a moisture transmission rate or an oxygentransmission rate of the barrier material is equal to or less than about0.1 cc/m2/day.
 2. The backlight unit of claim 1, wherein the lightconverting layer further comprises: a transparent substrate, a lightconverting film on a surface of the transparent substrate, andcomprising the semiconductor nanocrystals, and a barrier layer on asurface of the light converting film, and comprising the barriermaterial.
 3. The backlight unit of claim 2, wherein the barrier layer isfurther on a surface of the transparent substrate, opposite to thesurface of the light converting film.
 4. The backlight unit of claim 1,wherein the light converting layer further comprises: a light convertingfilm comprising the semiconductor nanocrystals, and a barrier layer on asurface of the light converting film, and comprising the barriermaterial.
 5. The backlight unit of claim 1, wherein the light convertinglayer further comprises a light converting film comprising thesemiconductor nanocrystals and the barrier material.
 6. The backlightunit of claim 5, wherein the light converting layer further comprises abarrier layer on a surface of the light converting film, and comprisingthe barrier material.
 7. The backlight unit of claim 6, wherein thebarrier material of the light converting film restricts penetration ofone of the moisture and the oxygen, and the barrier material of thebarrier layer restricts penetration of the other of the moisture and theoxygen.
 8. The backlight unit of claim 1, further comprising a pluralityof light converting layers which converts the light into light ofdifferent colors.
 9. The backlight unit of claim 8, wherein theplurality of light converting layers are arranged to have an emissionwavelength with lower energy as a distance from the light sourcedecreases.
 10. The backlight unit of claim 8, wherein the plurality oflight converting layers is spaced apart from one another, and a blanklayer is defined between adjacent light converting layers of theplurality of light converting layers.
 11. The backlight unit of claim 1,wherein the barrier material comprises at least one selected from anorganic material and an inorganic material.
 12. The backlight unit ofclaim 11, wherein the barrier material comprises the organic materialand the inorganic material repeatedly alternated in a stack.
 13. Thebacklight unit of claim 11, wherein the organic material comprises atleast one selected from thiolene, hybrid epoxy, polyurea,polytetrafluoroethylene, polydimethylsiloxane, polyvinylchloride,polycarbonate, polystyrene, polyimide, parylene, polyethylacrylate, andpolymethylmethacrylate, and the inorganic material comprises at leastone selected from silicon oxide, aluminum oxide, titanium oxide, indiumoxide, tin oxide, indium oxide, tantalum oxide, zirconium oxide, andniobium oxide.
 14. The backlight unit of claim 1, further comprising adiffusive plate between the light source and the light converting layer,or between the light converting layer and the liquid crystal panel. 15.The backlight unit of claim 14, wherein the light converting layercontacts a surface of the diffusive plate.
 16. The backlight unit ofclaim 1, wherein the light converting layer further comprises lightdiffusing particles which diffuse the light.
 17. The backlight unit ofclaim 16, wherein the light converting layer further comprises: alight-converting diffusive film comprising the semiconductornanocrystals and the light diffusing particles, and a barrier layer on asurface of the light-converting diffusive film, and comprising thebarrier material.
 18. The backlight unit of claim 16, wherein the lightconverting layer further comprises a light-converting diffusive filmcomprising the semiconductor nanocrystals, the barrier material and thelight diffusing particles.
 19. The backlight unit of claim 18, whereinthe light converting layer further comprises a barrier layer on asurface of the light-converting diffusive film, and comprising thebarrier material.
 20. The backlight unit of claim 1, further comprisingan adhesive layer on a side surface of the light converting layer, andcomprising the barrier material.
 21. The backlight unit of claim 1,further comprising a light guide plate between the light source and thelight converting layer, wherein the light guide plate guides the lighttoward the light converting layer.
 22. The backlight unit of claim 21,wherein the light guide plate comprises a light emitting first surface,a second surface opposite to the light emitting first surface, and aside surface connecting the first and second surfaces to each other, andthe light source faces the side surface of the light guide plate. 23.The backlight unit of claim 1, further comprising an optical sheetbetween the light source and the liquid crystal panel, and comprising atleast one selected from a prism sheet, a brightness enhancement sheetand a micro-lens sheet.
 24. The backlight unit of claim 1, wherein thelight source emits blue light or ultraviolet light.
 25. The backlightunit of claim 1, wherein the light source comprises: a substrate, and aplurality of light-emitting diodes on the substrate.
 26. A liquidcrystal display device comprising: a light source comprising alight-emitting diode which generates and emits light; a light convertinglayer spaced apart from the light source, wherein the light convertinglayer converts the light from the light source into another light andoutputs the another light toward a liquid crystal panel, the lightconverting layer comprising: semiconductor nanoparticles, and a barriermaterial which restricts penetration of moisture or oxygen; and theliquid crystal panel which forms an image using the another light fromthe light converting layer, wherein a moisture transmission rate or anoxygen transmission rate of the barrier material is equal to or lessthan about 0.1 cc/m2/day.
 27. The liquid crystal display device of claim26, wherein the light converting layer further comprises: a transparentsubstrate, a light converting film on a surface of the transparentsubstrate, and comprising the semiconductor nanocrystals, and a barrierlayer on a surface of the light converting film, and comprising thebarrier material.
 28. The liquid crystal display device of claim 27,wherein the barrier layer is further on a surface of the transparentsubstrate, opposite to the surface of the light converting film.
 29. Theliquid crystal display device of claim 26, wherein the light convertinglayer further comprises: a light converting film comprising thesemiconductor nanoparticles, and a barrier layer on a surface of thelight converting film, and comprising the barrier material.
 30. Theliquid crystal display device of claim 26, wherein the light convertinglayer further comprises a light converting film comprising thesemiconductor nanocrystals and the barrier material.
 31. The liquidcrystal display device of claim 30, wherein the light converting layerfurther comprises a barrier layer on a surface of the light convertingfilm, and comprising the barrier material.
 32. The liquid crystaldisplay device of claim 26, wherein the barrier material comprises atleast one selected from an organic material and an inorganic material.33. The liquid crystal display device of claim 26, further comprising adiffusive plate between the light source and the light converting layer,or between the light converting layer and the liquid crystal panel. 34.The liquid crystal display device of claim 26, wherein the lightconverting layer further comprises light diffusing particles whichdiffuse the light.
 35. The liquid crystal display device of claim 34,wherein the light converting layer further comprises: a light-convertingdiffusive film comprising the semiconductor nanocrystals and the lightdiffusing particles, and a barrier layer on a surface of thelight-converting diffusive film, and comprising the barrier material.36. The liquid crystal display device of claim 34, wherein the lightconverting layer further comprises a light-converting diffusive filmcomprising the semiconductor nanocrystals, the barrier materials and thelight diffusing particles.
 37. The liquid crystal display device ofclaim 26, further comprising a light guide plate between the lightsource and the light converting layer, wherein the light guide plateguides the light emitted from the light source toward the lightconverting layer.
 38. The liquid crystal display device of claim 37,wherein the light guide plate comprises a light emitting first surface,a second surface opposite to the light emitting first surface, and aside surface connecting the first and second surfaces to each other, andthe light source faces the side surface of the light guide plate.